Enterprises commonly maintain multiple copies of important data and expend large amounts of time and money to protect this data against losses due to disasters or catastrophes. One challenge is how to create a copy of an existing large database to a backup database.
To build a backup database, one conventional approach takes the primary or source database off-line (i.e., shuts it down) and then moves data from the primary database to the backup or target database. Another approach moves a copy of data from the primary database to the backup database and later updates the backup database with changes that occurred while the data was being copied and moved.
These conventional approaches are deficient. Some enterprises, such as financial institutions, airline industry, and others, would lose valuable time and money if the primary database were taken offline or shutdown. Simply copying and moving data are also problematic since these require significant storage for transactions logs that accumulate during the copying process. In large database systems, these transaction logs can grow beyond the storage capacity to be retained or grow to a size wherein updates cannot be applied in a timely manner. Basically the backup system falls behind and never catches up to the primary system.